1. Field of the Invention
The invention relates to an image processing method, and more particularly to an image processing method of contrast enhancement.
2. Description of the Related Art
Contrast is the difference in visual properties that makes an object (or its representation in an image) distinguishable from other objects and the background. In visual perception of the real world, contrast is determined by the difference in the color and brightness of the object and other objects within the same field of view. Contrast enhancement is one of the image enhancement techniques used to enhance the contrast presented in an image based on a contrast curve. Global contrast enhancement of an image uniformly adjusts the contrast of each pixel of the image according to a global contrast curve. However, local features are often sacrificed when the features are small with corresponding pixel values not dominating the average pixel value of the image. Local contrast enhancement is another image enhancement technique to divide the image into several local partitions (i.e. blocks) and enhance the contrast of each image partition independently. Local features in each image partition are preserved due to the merit of the locally enhanced contrasts. However, the output image may not be satisfactory due to the lack of a global view of the image.
In addition, complex computations using digital image data cause the number of data bits to increase. However, the flat panel displays (FPDs) have a finite number of input data bits, for example, 6 or 8 bits. To implement a display system based on complex computations, data quantization is indispensable. However, data quantization causes image data degradation.
Therefore, a contrast enhancement method giving consideration to both the global and local characteristics of an image to generate a satisfactory enhancement result is required.